> From: Adam Maloney <adamm at sihope.com>

> Yes, it's very true.  I'm no physics geek, but at 52x the angular
> velocity (?) is great enough to tear CD's apart.  I forget the numbers,
> but basically you've got some ridiculous amount of force at the outer
> edge of the disc, basically trying to pull it apart.  At 52x (or even
> 48x) with a flimsy disc (low quality, weak, defective, or broken
> somehow), this is likely to happen.  

You may not be, but there should be quite a few on the list. Let's do
some math!

Audio CD's start at 500 RPM and slow down to 200 RPM. That's 1x.
The fast drives go CAV at one speed, and are fastest at the end of
a disc, so let's go with 52x200 or 10,400 RPM.

The speed of the edge of a disc v=wr which is the rotational
speed times the radius, or 10400RPM * 6cm or 62400cm/min or
(uhm... times 1min/60s times 1m/100cm) 10.4m/s (!) or
62400 cm/min (times 60min/1hr times 1mi/160934cm) = 23.26 mph.

CD's have a mass of about 20g. A 1g chunk at 10.4m/s should
have 1/2 * m * v * v energy or about 1/20 (need help with unit
here...) joule? Or the same energy as a kilogram dropped from
a height of 5.5mm. (U = mgh)

Still, I wouldn't want it headed for MY eye.

Chris


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